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Chapter - 8.ppt-BB - 2012

Adjacent 1 segregation adjacent non homologous

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Unformatted text preview: ontain a complete set of genes and are thus viable Both have duplications and deletions and are thus unviable 3. Adjacent-2 segregation Adjacent homologous chromosomes segregate into the same cell Leads to unbalanced gametes Both have duplications and deletions and are thus unviable VARIATION IN CHROMOSOME NUMBER NUMBER Chromosome numbers can vary in two main ways Chromosome Euploidy Aneuploidy Variation in the number of complete sets of Variation chromosome chromosome Variation in the number of particular chromosomes Variation within a set within Euploid variations - animals occasionally - frequently in plants frequently Aneuploid variations - abnormal conditions Aneuploidy The phenotype of every The eukaryotic species is influenced by thousands of different genes different Aneuploidy commonly causes Aneuploidy an abnormal phenotype an Aneuploidy The harmful effects of aneuploidy were first discovered in the 1920s The by Albert Blakeslee and his colleagues by Jimson weed (Datura stramonium) All of its 12 possible trisomies produce capsules (dried fruit) that All are phenotypically different are the aneuploid plants have other morphologically distinguishable the traits traits Including some detrimental ones Some human aneuploidies are Some influenced by the age of the parents influenced Euploidy Most species of animals are diploid In many cases, changes in euploidy are not tolerated Some euploidy variations - naturally Some occurring occurring In many animals, certain body tissues display normal In variations in the number of sets of chromosomes variations Diploid animals sometimes produce tissues that are Diploid polyploid polyploid This phenomenon is termed ______________ Liver cells, for example, can be triploid, tetraploid or even Liver octaploid (8n) octaploid Polytene Chromosomes Occur mainly in the salivary Occur glands of Drosophila and a few Drosophila other insects other Chromosomes undergo Chromosomes repeated rounds of chromosome replication without cellular division without In Drosophila, pairs of In Drosophila pairs chromosomes double approximately nine times (29 = 512) (2 This bundle is termed a This ______________. ______________. Euploidy - Plants In co...
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